Adjustable tracer finger



Aug. 26, 1952 A. PETERSON ET AL ADJUSTABLE TRACER FINGER Filed Jan. 15,1950 N mw RH N E ETV VEN m AT VI NA L WC Patented Aug. 26, 1952 ADJUS'TABLE TRACER FINGER Lynn A. Peterson, Burbank, and Clayton V.

Huber, Los Angeles, Calif., assignors to Lockheed Aircraft Corporation,Burbank, Calif.

Application January 13, 1950, Serial No. 138,402

4 Claims. (01. 3323) This invention relates to machine tools and relatesmore particularly to tracer fingers for use in duplicating machines, pinrouters, spar mills, lathes, and other machine tools where a tracerfinger is moved along a template, orthe like, to govern the motion of acutting tool and thereby produce a cut corresponding with the contour ofthe template.

Many types of machine tools are controlled by mechanisms having atemplate and a finger or roller which moves along or upon the templateto govern the motion of a cutter so that the course or path of thecutter is determined by the contour or configuration of the template.With such machines the size of the finished part or the nature of thecut to be made is de termined not only by the size and shape of thetemplate but also by the size of the cutter and the size of the fingerwhich moves on the template, it being necessary that the tracer fingerbe of the same diameter as the cutter or of a given size with relationto the cutter. There arc, of course, many sizes of cutters used on agiven machine tool and cutters of only slightly different effectivediameters are used for rough cuts and finish cuts in any given series ofop erations. Furthermore, reconditioning or sharpening of the cuttersusually reduces their effective cutting diameters. Because of thesefactors it has, in the past, been necessary to stock and maintain alarge number of tracer fingers graduated or varying only slightly indiameter and quite frequently a machine tool remains idle while a tracerfinger of the required size is being obtained or made specially for agiven job.

It is a general object of the present invention to provide a practical,efiective adjustable or variable diameter tracer finger. The tracerfinger of the invention may be set or operated to have effective oroperating diameters within a-considerable range thereby markedlyreducing the number of tracer fingers required, assuring closertolerances during the cutting or machining operations, and effectingeconomy in the operation of the machine. 7

It is another and important object of the invention to provide avariable diameter tracer finger incorporating a micro adjustment meanswhereby the effective diameter of the finger may be easily, quickly andaccurately adjusted by simple turning or angular movement of acalibrated dial and then set or locked in the adjusted position.

Another object of the invention is to provide an adjustable or variablediameter tracer finger of the character mentioned that is small andcompact and of such construction that it may beinstalled in the tracerhead in the usual manner to cooperate with conventional templates. Thedevice does not include bulky or projecting parts to interfere with itsinstallation in the tracer head or with its proper cooperation with thtemplate.

It is a further object of the invention to pro--' vide an adjustabletracer finger of this class that is simple and inexpensive tomanufacture and that may be supplied with template engaging rolls of anyrequired range of sizes.

Other objectives and features of the invention will become apparent fromthe following de-v tailed description of typical preferred embodi-.ments throughout which description reference will be. made to theaccompanying drawings in which: V V

Figure 1 is a perspective viewillustrating a tracer finger of theinvention operating in a template and controlling a cutting head, withparts of the machine tool being illustrated schematically;

Figure 2 is an enlarged side elevation of the tracer finger appearing inFigure 1;

Figure 3 is a vertical detailed sectional view of the tracer finger withthe mandrel appearing in side elevation;

Figure 4 is a transverse detailed sectional-view taken as indicated byline 44 on Figure 3; I

Figure 5 is a fragmentary sectional view illus-" trating a modified formof construction; and.

Figure 6 is a view similar to Figure 3 illustrating another embodimentof the invention.

The devices of the invention may, of course, be designed and constructedfor use with given or special machines and may be modified to adapt themfor such applications. In the follow? ing description we will describethe typical embodiments of the device illustrated in the accompanyingdrawings, it being understood that the invention is not to be construedas limited or restricted to the particular details or application setforth.

In Figure 1 there is illustrated a workpiece W and a cutter C actingupon the workpiece. The

cutter C is carried by a rotating shaft or spindle I0 which in turnforms a part of a movable cutting head H. A template T is mounted forengagement by the tracer finger of the invention which is adapted to beremovably secured in a tracer head H. The broken line M in Figure 1represents the mechanism interconnecting the cutting head H and thetracer head H whichmechanism forms a part of th machine tool and may bea mechanical, hydraulic or electrical instrumentality which causes thehead II to follow a path identical with the path of movement of thetracer head H as determined by the movement of the tracer finger alongthe template T. As such mechanisms are well known to those skilled inthe art the mechanism M has been indicated in the drawings in aschematic manner. The template T may either be of the internal type asillustrated or may be of the external type and, of course, its activesurface S may be of any required configuration.

The tracer finger of our invention as illustrated in Figures 1 to 4inclusive may be said to comprise generally a stem or mandrel I2, ashell I3 screw threaded on the mandrel for axial adjustment thereon, anda template engaging means I6 associated with the shell I3 and coop'erating with the mandrel I2 to be shifted or adjusted radiallyuponrelative axial movement between the mandrel and shell.

The mandrel I2 isan elongate part and forms the central or innerielementof the finger assembly. In practice the mandrel I2 may be a one-piecemember and is provided with an upper or outer end portion in the form.of a shank I adapted to be removably secured inthe tracer head H. Theportion IE of the mandrel I2 below theshank I5. is enlarged indiame'terto carry theshell I3 as will be later described. Atapered or'conicalsurface-I1 is provided on the mandrel I2 between the shank I5 and theenlarged portion I6. The part of the mandrel I2 which continuesdownwardly or, forwardly from the enlarged portion I6 is characterizedby cylindrical landsIBspaced apartbyareas I 9 of reduced diameter, thelands serving to support or stabilize the shell I3 as will later becomeapparent. The lower-end of the mandrel I2 is provided with ataperedorjconical surface forv cooperating withQthetmplate engagingmeans I4. Thesurface 20 is preferably .of vsubstantiallength but mayterminate at the flat small diametered end face of the mandrel. Whilethe inclination of the surface 20 may be varied in different devices ofthe invention wehave found it desirabl to form the surface to have anincluded angle of approximately 43. It is to be.understood that theenlarged diametered portion IS, the lands I8, and theconical surface 26,are all concentric with, the central longitudinal axis of themandrel1.2.. 1

The shell I3 is preferably, though not necessarily; a one-piece memberand istubular to enclose or surround the major portion of the mandrelI2.r The internal surface of the shell I3 rotatably bears on thecylindrical lands I8 of the mandrel and carries a thread for cooperatingwith a matingt'thread on the mandrel portion IS. The screw threads atthe portion I5 may, in practice, be No. v4O threads. The upper partof..theshell I3 may have increased wall thick: ness .and is preferablyexternally knurled or roughened to facilitate manual turning oradjustment. The upper or outer endof the shell I3 presents an inclinedor conical surface 2I whichmayv have thesame inclination as the adjacentmandrel surface I'i'. The surface 2:! is provided with a number ofequally spaced, axial calibrations 22 for cooperating with a singleaxial mark.23 .onv the mandrel surface IT to constitute a microindicating means for indicatingthe radial adjustment or position of thetemplate-engaging means I4. A set screw or lock screw 25 is threadedthrough a radial opening in the wall of the shell I3 and its inner endis adapted to cooperate with a surface I9 of the mandrel I2 to set orlook the shell I3 in any selected adjusted position. The shell I3continues downwardly or forwardly beyond the conical mandrel surface 20and is provided at its end with an internal annular flange 24 presentinga concentric internal surface and a flat normal upper or inner surface.

The template engaging means I4 serves to ride on the surface S of thetemplate '1 to guide or direct the cutter C through the medium of themechanism M and in accordance with the invention the active or effectiveradial position of the means. I 4 may be varied or adjusted by angularmovement of the shell I3 to regulate the eflective diameter of thetracer finger. The means I t includes a socket member 26 for engagingthe conical surface of the mandrel I2 and carrying a roller 21 forriding on the'template surface S. The socket member 23 is containedwithin the shell I3 and has an opening or socket 28 in its inner end forreceiving the conical end of the mandrel I2. In the structureillustrated in detail in Figure 3 the socket 28 is conical and its wallhas substantially the same pitch or inclination as the surface 20.However, themean diameter of the socket 23 is considerably larger thanthe. mean diameter of the mandrel surface 2.0 so that the member 28 is.

The forward or outer end of the socket mem ber 26 has a trunnion'orshaft 30 of reduced diameter carrying the roller 27. A screw 3I isthreaded in a central opening in the shaft 30 and its head retains. theroller 2'! on the shaft 30. The roller 27. may befree to rotate on theshaft 30 as a result of its cooperation with the template surface S orthe roller may be tightly clamped on the shaft 30in which case thesocket member '26 turns on the conical surface 20 of the mandrel I2. andreplacement of the roller 21 radial openings 32 are provided in the wallof the shell I3 and in the socket member 26 to receive a pin or'wrenchfor holding the member 26 against rotationwhen the screw 3I is beinginstalled and removed. In

Figures 3 and 4. we have shown a wrench in the form of a spring 33shaped to fit about the shell I3 and provided with diametrically alignedpins ally ,with the conical surface 20 of the mandrel- In-order tofacilitate removal tive diameter of the finger.

l2, the wall of the socket is convert to have only substantiallypointcontact with the mandrel surface 20 with the member 26 in any adjustedposition. The structure of Figure 5 is somewhat simpler to manufacturethan the arrangement illustrated in Figure 3.

It is believed that the operation of the tracer finger illustrated inFigures 1 to. 4 inclusive will be understood from the foregoing detaileddescription. Assuming that a roller 21 of selected diameter-issecured onthe member 26 and assuming that the setscrew 25 has been loosened, theshell |3 may be rotated relative to the mandrel-'|2. to adjust theefiective diameter of the finger as required. It will be seen that uponangular'movement of the shell l3 in one directionthe socket member 26 ismoved upwardly on the conical surface 20 so that the member andits,;template'engaging roller 21 are moved or adjusted radially outwardto increase the effec- On the other hand, when the shell I3 is turned inthe other direction the socket member 26 is moved downwardlyon theconical surface 20 to adjust the roller 21 radially inward to decreasethe effective diameter of the finger. Following such an adjustment thescrew 25 is tightened to lock or set the parts in the adjustedpositions. When the tracer finger is in operation the engagement of theroller 21 with the surface S of the template T holds the wall of thesocket 28 against one side of the conical mandrel surface 20, the wallof the socket being spaced from other parts of the conical surface. Thisrelationship is clearly illustrated in'Figure 3. As theroller 21 is atall times urged against the template surface S the engagement of thesocket 28 with the surface 20 is uninterrupted. It will be apparent thatby properly relating the threads on the mandrel part l6 and shell I3,the inclination of the surface 20 and the spacing of the calibrations22, simple adjustment of the calibrations 22 relative to the mark 23will effect a given radial adjustment of the roller 21. Furthermore, theparts may be related and proportioned so that the finger has asubstantial range of adjustment reducing the number of fingers that arerequired for a full range of cutter sizes etc. The screw 25 at thereduced area l9 serves to limit relative threading of the mandrel 20 andshell l3 to prevent unintentional disassembly of the device.

Figure 6 illustrates another and simplified form of the invention. Thisadjustable tracer finger includes a mandrel 40, a stem 4| adjustablyscrew threaded with the mandrel 40 and presenting a conical surface 42and template engaging means in the form of a roller 43 cooperating withsaid surface 42 and held in cooperation with the mandrel 40 to beadjusted radially upon relative axial movement between the mandrel andstem.

The mandrel 40 has a shank 44 of reduced diameter adapted to be securedin the tracer head H. The forward or lower end of the mandre1 40 has acentral longitudinal opening 45 and the entrance to this opening may bein the form of an enlarged socket.

The above mentioned stem 4| has its inner portion adjustably screwthreaded in the opening 45 of the mandrel and has an unthreadedintermediate portion 41 of somewhat enlarged diameter received in theabove mentioned socket part of the opening 45. The conical surface 42 ofthe stem 4| continues downwardly or outwardly from the portion 41 andthe outer part 48 of the stem terminates in a knurled head or knob 49 6,for facilitating manualradjustment of the stem; A set screw or lookscrew 50 is threaded in a radial opening in the wall of the mandrel 40and is engageable with the intermediate portion 41 of the stem 42 to setor look the stem in its adjusted position.

The template engaging roller 43 is arranged at the lower or forward endof the mandrel; 40*.to surround the conical surface 42. The'externalsurface of the roller 43 is cylindricalto'conform with the surface S ofthe templateT. 'Theopen ing 5| in the roller 43 is preferably conica'l"to conform with the stem surface 42 although the mean diameter of theopening 5| in theroller is considerably larger than the mean diameterof; the conical surface 42. A flanged sleeve52 arranged on the stemportion 48 anda coiled spring 53 is engaged under compression betweenthe knurled head 49 and the sleeve to urge the sleeve and the roller 43upwardly so that the roller is at all times held against the end ofthe-mandrel 40. This maintains the roller 43 in its active position. Thespring 53 maintains the sleeve :52 against the lower or outer side ofthe roller 43- where it prevents cutting-s from entering the roller andthe mandrel 40.

It will be seen that upon loosening the screw 50 the stem 4| may bethreaded or adjusted axially relative to the mandrel 40 and roller43.Such axial adjustment of the stem 4| moves the conical stem surface 42either inwardlyorgoutwardly with respect tothe roller 43 to. change theeffective diameter of the tracer finger by shifting the roller 43radially inward 0r outward as the case may be. Following such adjustmentthe screw 50 is tightened to lock or setthe' parts in the adjustedposition. In the operationof the tracer finger the roller 43 is at alltimes urged against the surface S of the template T so that the wall ofthe tapered opening 5| in the roller presses against or rides on oneside of the conical stem surface 42, as clearly illustrated in Figure 6,but the roller 43 is free to rotate on the surface 42 so that any minorwear that may accompany the operation of the tracer finger is welldistributed.

Having described only typical forms of the invention we do not wish tobe limited to the specific details hereinset forth, but wish to reserveto ourselves any variations or modifications that may appear to thoseskilled in the art and fall within the scope of the following claims.

We claim:

1. A tracer finger comprisinga mandrel having a substantially conicalsurface, :a member having an opening surrounding at least a portion ofthe mandrel to receive said surface, the opening having an averagediameter greater than the average diameter of said surface so that thewall of the opening is engageable with a side region of the surface tosupport the member against lateral pressure, the wall of the openingbeing convexly curved to have substantially point contact with saidsurface, a part on the member adapted to press laterally against a faceto be traced, the part and said member constituting an assembly that isaxially movable relative to the mandrel, a shell movable on the mandreland connected with said assembly to move the same axially therewith inboth axial directions relative to said surface to adjust the memberlaterally, and means for moving the shell axially of the mandrel.

2. A tracer finger comprising a mandrel having a substantially conicalsurface, means for aeoneee engaging asi'ace to be traced and having anopening-surrounding at least aportionof the mandrel to receive'saidsurface, the opening having an average diameter greater than the averagediameter of said surface so that the wall of the opening is engageablewith a side regioniof the surface to support the means againstlateral=pressure, a surface on said means adapted topress laterallyagainst the face'to be traced,a shell on the mandrelassociated therewithfor axial movementthereon, cooperating surfaces on said means and shellconnecting saidmeans with the shell for" positive axial 'movementtherewith in both directions and relative to said surface so that saidsurface adjusts said means laterally of the man drelf and mating screwthreads on the mandrel and shell operable to move the shell axially uponrotation of the shell. 7 a

3. A tracer fingerfor following a surface including a mandrel having aconical part, a member having a generally iconicalopening for re-'ceiving" said part, the average diameter of the opening being largerthanthe average diameter of saidpart so that the Wflll'Of said openingis adapted to engage a side portion of said partja shell movable on themandrel and cooperating with said member 'to move the same axiallytherewith in one direction, a roller rotatable on said member forengaging "said surface, means re' straining the roller against axialmovement on the member, cooperating surfaces on the shell and rollerwhereby'the shell is operable to move the roller and member axially inthe other direction, mating screw threads on the mandrel and shelloperable upon angular movement of the shell to move the'shell and memberaxially of the mandrel and thus move th member axially on saidconicalpart to adjust the member aterally, and means for securing the shellagainst angulafmovement with the member in selected adjusted positions.4'. A tracer finger for following a surfaceineluding a mandrel having aconical part, a member having a generally conical opening for re.-ceiving .said' part, the average diameter of the opening being largerthan theaverage diameter of said part so-"that the wall of .said openingis adapted to engage aside portion of said part; the wall-of the openingbeing convexlycurved to have substantially point contact with said part,aashell movable on the'mandrel and cooperating with saidmember tomovethe same axially therewith, a'rollerion said member for engaging saidsurface, rmating screw threads on the mandrel andishell operable uponangular movement of the'shell to move the shell and member axially ofthe mandrel and thus move the member axially on said conical part toadjust the member laterally, and means for securing the shell againstangular movement with the member in selected adjusted-positions. 7 LYNNA} PETERSON.

CLAYTON V. HUBER.

REFERENCES CITED The following references are of recordfin the file ofthis patent:

UNITED STATES. PATENTS Number Name Date 1,840,853 Shaw et' al. Jan. I2,1932 2,225,717 Shaw Dec. 24, 1940 2,397,108 Hanna et 'al.' Mar; 26, 1946assume- "Klema i June-19,1951

